1. Technical Field
The present invention relates to trimming materials (upholstery) for automobiles, and in particular to trimming materials that has a surface skin (covering) material and a base material bonded to each other via a colored resin film interposed therebetween.
2. Description of the Related Art
Japanese Laid-Open Patent Publication No. 6-278260 teaches a known trimming material. This known trimming material is shown in a vertical cross sectional view in FIG. 5(A) and is labeled with reference numeral 50. The known trimming material 50 comprises a base material, e.g., a felt sheet, a resin film 53, and a surface skin material 55 that may be made of non-woven fabric. The resin film 53 is colored to be similar to the color of the surface skin material 55. The resin film 53 may be melted by heat, so that the resin film 53 can partly impregnate into the rear surface of the surface skin material 55 and into the front surface of the base material 51, as shown in FIG. 5(B). The surface skin material 55 and the base material 51 are then pressed from opposing sides, so that the surface skin material 55 and the base material 51 may be bonded to each other by the resin film 53 as indicated by two-dotted chain lines in FIG. 5(B). Because the color of the resin film 53 is similar to the color of the surface skin material 55, the base material 51 may not be easily seen from the side of the surface skin material 55, even if the surface skin material 55 has a relatively thin thickness for the overall purpose of reducing trimming material weight.
The manufacturing process of the known trimming material 50 includes the step of simultaneously impregnating the melted resin film 53 into the upper surface skin material 55 and into the lower base material 51. Therefore, when the melted resin travels upwards and downwards, it is likely that a plurality of pinholes 53p are formed in the resin film 53 extending throughout the thickness of the resin film 53 as illustrated in FIG. 5(B). The pinholes 53p thus formed may not be completely removed even after the surface skin material 55 and the base material 51 have been pressed from opposite sides as indicated by two-dotted chain lines in FIG. 5(B). The pinholes 53p may give a mottled appearance to the resin film 53. Therefore, when the surface skin material 55 is very thin, the mottled appearance of the resin film 53 may be seen through the surface skin material 55. As a result, the appearance of the trimming material 50 may be degraded, as viewed from its ornamental surface, i.e., the front surface of the surface skin material 55.